Hagman I was wondering how the conversion is going I am very interested in doing the same swap. From what I have read going MPFI does not help on the top end; the boat's low RPM torque and manners are much improved. I was told that start up and warm up is a breeze with MPFI. I would not recommend just installing an unmodified car ECU. The load levels on a road going car are different from a boat. I think factory automotive fuel maps will make your boat dangerously lean at lower RPM's; on a car the fuel maps take very little feed back from the O2 sensors until it reaches operating temp appox 185. On a raw water boat that is to high and needs to be adjusted to 160 so the boat goes in to closed loop at that temp. I have found an adaptor to run a truck or van lower intake and mate it with a 5.0 upper.
http://www.bcbroncos.com/store/product_info.php?cPath=131_108&products_id=1059
I have been considering modifying a foxbody mustang harness with a microsquirt so these parameters can be set.